STRUCTURAL AND LATTICE DYNAMICAL INVESTIGATION OF MODELS FOR REACTIONS IN ORGANIC-CRYSTALS

The topochemical postulate and phonon assistance are two models used for understanding solid-state reactions. Neither has been studied in a fashion that directly relates the two. This research reports a concerted X-ray crystallographic and polarized, single-crystal Raman scattering study which investigates the models' applicability in a partially reacted crystal of 2,5-distyrylpyrazine, a prototypical reacting organic solid. The structural results of a partially reacted monomer crystal are related to the change in lattice dynamics observed by Raman scattering for the same system. By use of lattice dynamical calculations, the assignment of modes, and the structure of the partially reacted crystal, a detailed picture of the lattice motions and related displacements involved in the reaction is constructed and related to the topochemical postulate and the mechanism of phonon assistance.